Inaccurate performance data for BOB fighters in COD comparing to RL data

[TomcatViP]

In the series of " What archives tells us" here is the FLIGHT archives that I cited two days ago :

- There was no 100 octane fuel usage during BoB in the FC. Here I am putting my money on British pride that would hve pushed forward any of its usage (ok Brits are not French but never the less )

- in 1941 increased power Merlin's had 9lb boost level

- 100 oct fuel was used by some aircraft in the RN (Fulmar) fitted with special engines such as the Merlin VIII (presumably to compensate for the extra weight of the 2nd crew member and low alt missions)

- In 1941 planes were still using 87 octane such as was the Hurricane with Merlin XX

Sources : (http://www.flightglobal.com/pdfarchi...0-%201286.html)

1. "International power of the Merlin I and II was 950/990 h.p. at
2,600 r.p.m. at 12,250ft, and the maximum take-off output was
890 h.p. at 2,850 r.p.m."

2. Merlin III : "The power output of the standard engine,"
writes Harold Nockolds, "was 1,030 b.h.p. at 3,000 r.p.m. at
10,250ft with plus 6i lb boost. "

3. "the petrol normally used at that time was 87
octane"

4. "The Merlin II and I I I were installed in the Spitfire I, Defiant I,
Hurricane I, Sea Hurricane I, and Battle I, and were—as will
always be remembered—vital factors in the winning of the Battle
of Britain. The Merlin IV had pressure-water cooling in place
of the glycol cooling of the earlier models, and was developed
for installation in the Armstrong Whitworth Whitley IV bomber.
The Mk VIII, installed in the Fairey Fulmar I, was a medium supercharged
unit rated at 1,010 h.p. at 2,850 r.p.m. at 6,750ft,
and, using 100-octane fuel, delivered 1,080 h.p. at 3,000 r.p.m. for
take-off."

5. "The Merlin X—installed in the Halifax I, Wellington II and
Whitley V and VII—represented a very important advance in
that it had a two-speed supercharger to improve take-off, lowaltitude
performance during climb or level flight, and fuel
economy under cruising conditions. The speed change was
effected through an oil-pressure system, the actual changeover
under full power taking about a second. In low gear the Merlin X
gave 1,145 h.p. at 5,250ft, and in high gear 1,010 h.p. at 17,750ft."

6. "The Merlin XII, driving a Rotol three-blade constant-speed
airscrew, was installed in some Spitfire lls ; its maximum output
was 1,150 h.p. at 3,000 r.p.m. at 14,000ft and it had a 0.477:1
reduction gear."

7. "The next production-type engine was the Merlin XX, which,
compared with the X, delivered a greatly increased power at
height." [...] "Thus, using 100-octane fuel,
the international rating in low gear was 1,240 h.p. at 2,850
r.p.m. at 10,000ft and plus 9 lb/sq in boost; in high gear the
figure was 1,175 h.p. at 2,850 r.p.m. at 17,500ft, again at plus
9 lb boost."

8. "The Merlin XX powered the Beaufighter II, Defiant II, Halifax II and V, Hurricane II and IV, and Lancaster I and III."

9. "An increase in take-off output from 1,300 h.p. to 1,600 h.p. characterized
the Merlin 32, which powered the Barracuda II and
Seafire II."

10. "A variant which saw very extensive service was the Merlin 45,
fitted in the Spitfire V, P.R.IV and VII, and Seafire I I ; at 16,000ft
and 2,850 r.p.m. its output was 1,200 h.p. The Merlin 45M was
rated for duty at lower levels and delivered 1,585 h.p. at 2,750ft;
it was fitted in the Spitfire L.F.V"

11. "The Merlin 46 and 47 were
both high-altitude engines (1,115 h.p. at 19,000ft); the 46 powered
the Spitfire V, P.R.IV and VII, and Seafire I, and the 47 (which
had a cabin supercharger) found its application in the Spitfire VI."

12. "The key feature of the Merlin 61 was its two-speed, two-stage
supercharger, with two rotors on a common shaft. The mixture
was compressed by the first stage and was delivered to the inlet of
the second stage, where it was further compressed before being
delivered to the induction pipe. In order to reduce the mixture
temperature to a normal figure, a box-like intercooler was interposed
between the outlet of the second-stage supercharger and
the rear of the cylinder blocks. In a typical Spitfire installation
the intercooler radiator was mounted under the port wing in a duct, which also housed one of the main engine-cooling radiators."

13. "The real significance of the Merlin 61 was that at 40,000ft it
developed double the power given at a much lower altitude by the
Merlin II of 1939/40. Even at 23,500ft its maximum power was
1,390 h.p. The weight had risen to 1,640 lb."

14. The 67 had a reduction gear of 0.42:1 instead of 0.477:1,
as had the 63, 64 and 66, and the 68 was a Packard-built model,
designated V-1650-3 and installed in the Mustang I I I . Its takeoff
output was 1,400 h.p.

15. "The 67 had a reduction gear of 0.42:1 instead of 0.477:1,
as had the 63, 64 and 66, installed in the Mustang I I I . Its takeoff
output was 1,400 h.p. In the Merlin 69—another Packardbuilt
variant, known in America as the V-1650-7—1,490 h.p. was
available for take-off; this engine powered Mustang I l l s and IVs."

16. "The Merlin 130 and 131 were the first of their family to incorporate
downdraught carburettors; and, to eliminate the air scoop
as used on the Mosquito, ducted air intakes were faired into the
leading edges of the wing. The war-time Bendix/Stromberg
carburettor was replaced by a low-pressure fuel-injection system,
which delivered through a spray nozzle into the supercharger eye*.

17. The sum total of improvements incorporated
in these remarkable engines raised the output to 2,030 h.p. at
1,250ft with a boost of plus 25 lb/sq in.

18. Feel free to add your own episode !

*Ivan are your sure of your doc ?